1. Technical Field
The present invention relates in general to disk drives and, in particular, to an improved system, method, and apparatus for a slit shroud with an integrated bypass channel wall feature for disk drive applications.
2. Description of the Related Art
Generally, a data access and storage system consists of one or more storage devices that store data on magnetic or optical storage media. For example, a magnetic storage device is known as a direct access storage device (DASD) or a hard disk drive (HDD) and includes one or more disks and a disk controller to manage local operations concerning the disks. The hard disks themselves are usually made of aluminum alloy or a mixture of glass and ceramic, and are covered with a magnetic coating. Typically, one to six disks are stacked on a common spindle that is turned by a disk drive motor at several thousand revolutions per minute (rpm).
A typical HDD also utilizes an actuator assembly. The actuator moves magnetic read/write heads to the desired location on the rotating disk so as to write information to or read data from that location. Within most HDDs, the magnetic read/write head is mounted on a slider. A slider generally serves to mechanically support the head and any electrical connections between the head and the rest of the disk drive system. The surface of the slider facing the disk is aerodynamically shaped to create an air bearing in order to maintain a uniform distance from the surface of the rotating disk, thereby preventing the head from undesirably contacting the disk.
Typically, a slider is formed with an aerodynamic pattern of protrusions on its air bearing surface (ABS) that enables the slider to fly at a substantially constant height close to the disk during operation of the disk drive. A slider is associated with each side of each disk and flies just over the disk's surface. Each slider is mounted on a suspension to form a head gimbal assembly (HGA). The HGA is then attached to a semi-rigid actuator arm that supports the entire head flying unit. Several semi-rigid arms may be combined to form a single movable unit having either a linear bearing or a rotary pivotal bearing system.
The head and arm assembly is linearly or pivotally moved utilizing a magnet/coil structure that is often called a voice coil motor (VCM). The stator of a VCM is mounted to a base plate or casting on which the spindle is also mounted. The base casting with its spindle, actuator VCM, and internal filtration system is then enclosed with a cover and seal assembly to ensure that no contaminants can enter and adversely affect the reliability of the slider flying over the disk. When current is fed to the motor, the VCM develops a torque that is substantially proportional to the applied current. The arm acceleration is therefore substantially proportional to the magnitude of the current. As the read/write head approaches a desired track, a reverse polarity signal is applied to the actuator, causing the signal to act as a brake, and ideally causing the read/write head to stop and settle directly over the desired track.
In the prior art, a number of solutions have been proposed to enhance the air flow within hard disk drives, such as bypass channels located adjacent to the disk pack. For example, some disk drives have air guides that only guide a central portion of the flow of air back to the disks. Other disk drives have housings with doors that guide the flow of air from the disks to a filter, or they use diverter ramps that also only affect a central portion of the air flow.
For server class disk drive applications, the turbulence generated by the disk drive internal airflow is a significant contributor to the track misregistration (TMR) budget. To improve file performance and reliability, it is important to reduce the turbulence effects for the airflow around the HGA assembly. Two different techniques that are commonly used for turbulence reduction are the “dedicated flow bypass channel” and the “slit shroud.”
The dedicated flow bypass channel directs the upstream, highly turbulent airflow away from the HGA assembly region and returns it downstream of the HGA. The bypass channel is designed to have low resistance to airflow so that the extra motor torque needed to bypass the airflow around the HGA region is minimized. For effectiveness and manufacturing cost savings purposes, it is desirable to have the bypass channel designed into the base casting.
The purpose of the slit shroud is to maintain planar disk shrouding and to inhibit axial turbulent velocity components (i.e., relative to the planar orientation of the disks) that excite the HGA assembly. The slit shroud shields each individual suspension and the tail of the integrated lead suspension (ILS) from axial excitation from the mixing of highly turbulent radial flow coming off of the multiple spinning disks during operation. To increase the effectiveness of the slit shroud, the coverage area of the slit shroud adjacent the disks and HGAs must be maximized. Although these solutions are workable for some applications, other applications do not have sufficient coverage area for slit shrouds to operate effectively. Thus, an improved solution for disk drive applications having insufficient area to support conventional slit shrouds would be desirable.